Position estimation of a wireless terminal in a structure using base station signal information

ABSTRACT

Wireless terminals are provided that comprise, for example, a wireless signal receiving portion that receives a wireless signal transmitted from a base station; a measurement portion that performs signal intensity measurement of the wireless signal; and an information transmitting portion that transmits pieces of measurement information acquired by the signal intensity measurement, and at least one piece of base station identification information that indicates a base station of a transmission source of the wireless signal and that is associated with each of the pieces of measurement information. The wireless terminals may also comprise, for example, an input portion for specifying information on a section of a building structure; an information acquisition portion for acquiring and transmitting measurement information to a position estimation server; a display screen generation portion; a display portion; and a registration request portion for transmitting registration request information to a position estimation server.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/936,135filed Nov. 12, 2010, which is a National Phase application based onPCT/JP2009/057105 filed Apr. 7, 2009, and published as WO 2009/128364,which claims the benefit of priority of Japanese Application No.2008-109225, filed Apr. 18, 2008, all of which are incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates to an information processing device, aprogram, an information processing method and an information processingsystem.

BACKGROUND ART

Recently, a receiving device that can receive a wireless signaltransmitted from a satellite is equipped on a movable body, such as avehicle, a mobile phone and the like. Global positioning system (GPS)positioning enables estimation of the position of the movable bodyequipped with this type of receiving device. A position estimationtechnology that uses this type of receiving device is a common basictechnology that is important in a variety of fields includingnavigation, security, entertainment and the like.

Further, a position estimation method is also conceivable in which awireless terminal that performs wireless communication with a basestation (an access point) of a wireless local area network (LAN)measures a signal intensity of a signal transmitted from the wirelessbase station, and a position estimation device that can communicate withthe wireless terminal estimates the position of the wireless terminalbased on the signal intensity. For example, the wireless LAN basestation transmits a beacon at a constant frequency (for example, fivetimes per second) to notify a surrounding area of the existence of thewireless LAN base station. The wireless terminal transmits the signalintensity of the beacon to the position estimation device. The positionestimation device can estimate the position of the wireless terminalbased on the signal intensity and the position of the wireless LAN basestation that is registered in advance. With the above-described positionestimation method, the wireless LAN base station is provided also inindoor or underground environments. Therefore, it is possible to performposition estimation in indoor or underground environments, which isdifficult using the position estimation technology based on the GPSpositioning.

In this type of position estimation method, when a user carrying awireless terminal is present in a building or structure, not only thelatitude and longitude of the wireless terminal, but also informationindicating which floor of the building or structure the user iscurrently on is important. For example, Patent Document 1 discloses atechnology in which a wireless terminal measures signal intensities ofwireless signals transmitted from a plurality of base stations, and aposition estimation server estimates that the wireless terminal existson the floor of a base station that is a transmission source of awireless signal with a strong signal intensity.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2005-229617 (A)

SUMMARY OF INVENTION Technical Problem

However, the known position estimation technology simply estimates,based on the current signal intensity, the floor on which the wirelessterminal exists. Therefore, it is necessary to accurately register, inthe position estimation server, the floor on which each of the basestations exists.

The present invention is made in view of the above-mentioned issue, andaims to provide an information processing device, a program, aninformation processing method and an information processing system whichare novel and improved, and which are capable of estimating a positionof a wireless terminal in a building or structure even when a positionof each base station in the building or structure is not accuratelyregistered in advance.

Solution to Problem

According to the first aspect of the present invention in order toachieve the above-mentioned object, there is provided an informationprocessing device including: a storage portion that associates andstores section information indicating one section of a buildingstructure, first measurement information acquired by signal intensitymeasurement of a wireless signal transmitted from a surrounding basestation in a wireless terminal existing in the one section, and basestation identification information that identifies the base station; areceiving portion that receives, from a given wireless terminal, atleast one piece of second measurement information acquired by signalintensity measurement of a wireless signal in the given wirelessterminal, and at least one piece of base station identificationinformation that indicates a base station of a transmission source ofthe wireless signal received by the given wireless terminal and that isassociated with each of the at least one piece of second measurementinformation; a retrieval portion that retrieves, from the storageportion, at least one piece of first measurement information that isassociated with the at least one piece of base station identificationinformation received by the receiving portion; a selection portion thatselects section information that is associated with one of the at leastone piece of first measurement information, based on the at least onepiece of second measurement information received by the receivingportion and the at least one piece of first measurement informationretrieved by the retrieval portion; and a transmitting portion thattransmits, to the given wireless terminal, the section informationselected by the selection portion.

The information processing device may further include an evaluationportion that evaluates an acquisition position relationship between theat least one piece of first measurement information and the at least onepiece of second measurement information, based on the at least one pieceof first measurement information retrieved by the retrieval portion, andon second measurement information that is associated with the same basestation identification information as the at least one piece of firstmeasurement information, among the at least one piece of secondmeasurement information received by the receiving portion. The selectionportion may select, based on an evaluation result by the evaluationportion, section information associated with first measurementinformation that forms a pair with second measurement information suchthat the acquisition position relationship between the first measurementinformation and the second measurement information is relatively good.

For each of the at least one piece of first measurement informationretrieved by the retrieval portion, the evaluation portion maycalculate, based on the first measurement information, a first distancebetween an acquisition position of the first measurement information anda base station corresponding to the first measurement information. Foreach of the at least one piece of second measurement informationreceived by the receiving portion, the evaluation portion may calculate,based on the second measurement information, a second distance betweenan acquisition position of the second measurement information and a basestation corresponding to the second measurement information. Theevaluation portion may add the first distance and the second distancethat are calculated based on the first measurement information and thesecond measurement information that are associated with the same basestation identification information. The selection portion may selectsection information that corresponds to the first distance that has aminimum sum value when the second distance obtained by the evaluationportion is added thereto.

When the retrieval portion retrieves a plurality of pieces of firstmeasurement information that are associated with the same base stationidentification information and the same section information, theevaluation portion may compute an average value of sum values of thefirst distances and the second distance calculated based on theplurality of pieces of first measurement information associated with thesame base station identification information and the same sectioninformation and on the second measurement information. The selectionportion may select section information that corresponds to a piece ofthe first measurement information that is computed by the evaluationportion and that has a smallest average value or a smallest sum value.

The information processing device may further include a priorityprocessing portion that performs processing such that, as the number ofpieces of section information associated with the same base stationidentification information is larger, the section information isselected with priority by the selection portion.

According to the second aspect of the present invention in order toachieve the above-mentioned object, there is provided a program thatcauses a computer to function as: a receiving portion that receives,from a given wireless terminal, at least one piece of second measurementinformation acquired by signal intensity measurement of a wirelesssignal in the given wireless terminal, and at least one piece of basestation identification information that indicates a base station of atransmission source of the wireless signal received by the givenwireless terminal and that is associated with each of the at least onepiece of second measurement information; a retrieval portion that, froma storage medium that associates and stores section informationindicating one section of a building structure, first measurementinformation acquired by signal intensity measurement of a wirelesssignal transmitted from a surrounding base station in a wirelessterminal existing in the one section, and base station identificationinformation that identifies the base station, retrieves at least onepiece of first measurement information that is associated with the atleast one piece of base station identification information received bythe receiving portion; a selection portion that selects sectioninformation that is associated with one of the at least one piece offirst measurement information, based on the at least one piece of secondmeasurement information received by the receiving portion and the atleast one piece of first measurement information retrieved by theretrieval portion; and a transmitting portion that transmits, to thegiven wireless terminal, the section information selected by theselection portion.

According to the third aspect of the present invention in order toachieve the above-mentioned object, there is provided an informationprocessing method, including the steps of: receiving, from a givenwireless terminal, at least one piece of second measurement informationacquired by signal intensity measurement of a wireless signal in thegiven wireless terminal, and at least one piece of base stationidentification information that indicates a base station of atransmission source of the wireless signal received by the givenwireless terminal and that is associated with each of the at least onepiece of second measurement information; retrieving, from a storagemedium that associates and stores section information indicating onesection of a building structure, first measurement information acquiredby signal intensity measurement of a wireless signal transmitted from asurrounding base station in a wireless terminal existing in the onesection, and base station identification information that identifies thebase station, at least one piece of first measurement information thatis associated with the at least one piece of base station identificationinformation received in the receiving step; selecting sectioninformation that is associated with one of the at least one piece offirst measurement information, based on the at least one piece of secondmeasurement information received in the receiving step and the at leastone piece of first measurement information retrieved in the retrievingstep; and transmitting, to the given wireless terminal, the sectioninformation selected in the selecting step.

According to the fourth aspect of the present invention in order toachieve the above-mentioned object, there is provided an informationprocessing system that includes a wireless terminal and an informationprocessing device. The wireless terminal includes: a wireless signalreceiving portion that receives a wireless signal transmitted from abase station; a measurement portion that performs signal intensitymeasurement of the wireless signal received by the wireless signalreceiving portion; and an information transmitting portion thattransmits at least one piece of second measurement information acquiredby the signal intensity measurement of the wireless signal performed bythe measurement portion, and at least one piece of base stationidentification information that indicates a base station of atransmission source of the wireless signal and that is associated witheach of the at least one piece of second measurement information. Theinformation processing device includes: a storage portion thatassociates and stores section information indicating one section of abuilding structure, first measurement information acquired by signalintensity measurement of a wireless signal transmitted from asurrounding base station in a given wireless terminal existing in theone section, and base station identification information that identifiesthe base station; a receiving portion that receives, from theinformation transmitting portion of the given wireless terminal, the atleast one piece of second measurement information and the at least onepiece of base station identification information; a retrieval portionthat retrieves, from the storage portion, at least one piece of firstmeasurement information that is associated with the at least one pieceof base station identification information received by the receivingportion; a selection portion that selects section information that isassociated with one of the at least one piece of first measurementinformation, based on the at least one piece of second measurementinformation received by the receiving portion and the at least one pieceof first measurement information retrieved by the retrieval portion; anda transmitting portion that transmits, to the given wireless terminal,the section information selected by the selection portion.

According to the fifth aspect of the present invention in order toachieve the above-mentioned object, there is provided an informationprocessing system that includes a wireless terminal and an informationprocessing device. The wireless terminal includes: a wireless signalreceiving portion that receives a wireless signal transmitted from abase station; a measurement portion that performs signal intensitymeasurement of the wireless signal received by the wireless signalreceiving portion; an input portion to which section informationindicating one section of a building structure is input by a user; andan information transmitting portion that transmits at least one piece ofsecond measurement information acquired by the signal intensitymeasurement of the wireless signal performed by the measurement portion,and at least one piece of base station identification information thatindicates a base station of a transmission source of the wireless signaland that is associated with each of the at least one piece of secondmeasurement information. There is provided a receiving portion thatreceives, from the information transmitting portion of the wirelessterminal, the at least one piece of second measurement information, theat least one piece of base station identification information, and thesection information; a storage portion; and a recording portion thatassociates and records in the storage portion each of the at least onepiece of second measurement information, the at least one piece of basestation identification information associated with the secondmeasurement information, and the section information that are receivedby the receiving portion.

Advantageous Effects of Invention

As described above, according to the information processing device, theprogram, the information processing method and the informationprocessing system of the present invention, it is possible to estimate aposition of a wireless terminal in a building or structure even when aposition of each base station in the building or structure is notaccurately registered in advance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram showing an example of a configurationof a position estimation system according to a present embodiment.

FIG. 2 is a block diagram showing a hardware configuration of a positionestimation server.

FIG. 3 is a function block diagram showing configurations of theposition estimation server and a wireless terminal that are included ina position estimation system 1 according to the present embodiment.

FIG. 4 is an explanatory diagram schematically showing a cross sectionof a certain building or structure.

FIG. 5 is an explanatory diagram showing an example of signal intensityinformation that is acquired by signal intensity measurement at aposition P1.

FIG. 6 is an explanatory diagram showing an example of a floorinformation registration screen that is generated by a display screengeneration portion.

FIG. 7A is an explanatory diagram showing a specific example ofregistration request information that is transmitted from the mobileterminal at the position P1.

FIG. 7B is an explanatory diagram showing a specific example ofregistration request information that is transmitted from the mobileterminal at a position P2.

FIG. 7C is an explanatory diagram showing a specific example ofregistration request information that is transmitted from the mobileterminal at a position P3.

FIG. 7D is an explanatory diagram showing a specific example ofregistration request information that is transmitted from the mobileterminal at a position P4.

FIG. 8 is an explanatory diagram showing a specific example of a set ofbase station information that is registered in a storage portion.

FIG. 9 is an explanatory diagram showing a specific example ofmeasurement information that is transmitted from an informationacquisition portion at a position P5.

FIG. 10 is an explanatory diagram showing a specific example of anevaluation method by a distance evaluation portion.

FIG. 11 is an explanatory diagram showing specific examples of distanceevaluation by the distance evaluation portion.

FIG. 12 is a sequence diagram showing an operation flow of the positionestimation system according to the present embodiment.

FIG. 13 is a flow chart showing a detailed flow of estimation processingthat is performed by the position estimation server.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

Note that “embodiments to carry out the present invention” will bedescribed in the following order.

[1] Overview of position estimation system according to presentembodiment

[2] Detailed explanation of position estimation system according topresent embodiment

-   -   [2-1] Hardware configuration of position estimation server    -   [2-2] Registration of floor information    -   [2-3] Estimation of floor information

[3] Operation of position estimation system according to presentembodiment

[4] Conclusion

[1] POSITION ESTIMATION SYSTEM ACCORDING TO PRESENT EMBODIMENT

First, a position estimation system 1 according to a present embodimentwill be briefly described with reference to FIG. 1 and FIG. 2.

FIG. 1 is an explanatory diagram showing an example of a configurationof the position estimation system (information processing system) 1according to the present embodiment. As shown in FIG. 1, the positionestimation system 1 according to the present embodiment is provided witha communication network 12, a position estimation server 20, basestations 30A to 30C, and a wireless terminal 40. In FIG. 1, in order todistinguish each of the base stations, capital alphabetic characters areadded after the numerals, for example, the base stations 30A, 30B.However, when there is no need to particularly distinguish each of thebase stations, they are simply and collectively referred to as the basestation(s) 30.

The base station 30 relays communication between communication devicesthat are spatially dispersed. For example, the base station 30 can relaywireless communication between the wireless terminal 40 and anotherwireless terminal (not shown in the figures) that are within a radiowave reachable range, and can also relay communication between thewireless terminal 40 and a communication device that is connected bywire to the base station 30. More specifically, the base station 30 maybe a base station of a wireless local area network (LAN) based on theWireless Fidelity (WiFi) standard, may be a base station of the GlobalSystem for Mobile Communications (GSM), or may be a base station ofBluetooth.

The base station 30 can periodically transmit a beacon signal to notifysurroundings of the existence of the base station 30, in addition to asignal that is transmitted when the base station 30 relays wirelesscommunication. The beacon signal includes a base station ID serving asbase station identification information that is uniquely assigned to thebase station 30, for example. As a result, based on the base station IDof the received beacon signal, the wireless terminal 40 can confirm theexistence of the base station 30 that exists in the surrounding area.

The wireless terminal 40 can transmit and receive various types of databased on wireless communication controlled by the base station 30. Forexample, the wireless terminal 40 can receive content data from acontent distribution server (not shown in the figures) via the basestation 30, and can transmit and receive electronic mail to and fromanother wireless terminal (not shown in the figures). Note that thecontent data may include music data such as music, a lecture, a radioprogram, or the like, visual data such as a motion picture, a televisionprogram, a video program, a photograph, a painting, a diagram, or thelike, and any other data, such as a game, software, or the like.

Note that, in FIG. 1, a mobile phone is illustrated as an example of thewireless terminal 40. However, the wireless terminal 40 is not limitedto this example. For example, the wireless terminal 40 may also be apersonal computer (PC), a home video processing device (a DVD recorder,a video deck, or the like), a Personal Handyphone System (PHS), a mobilemusic playback device, a mobile video processing device, a personaldigital assistant (PDA), a home game console, a mobile game console, ahousehold electrical appliance, or the like.

Further, when the wireless terminal 40 receives a wireless signaltransmitted from the base station 30, the wireless terminal 40 measuresa signal intensity of the wireless signal, and associates the measuredsignal intensity with the base station ID of the base station 30,thereby transmitting it as signal intensity information to the positionestimation server 20 via the network 12. Note that the network 12 is awired or wireless transmission channel of information transmitted from adevice connected to the network 12. The network 12 may include, forexample, the Internet, a telephone network, a public circuit such as asatellite communication network, any kind of local area network (LAN)including Ethernet (registered trademark), or a leased line network,such as a wide area network (WAN), or an internet protocol-virtualprivate network (IP-VPN).

The position estimation server 20 stores base station informationincluding position information and the base station ID of each of thebase stations 30, and has a function to estimate the position of thewireless terminal 40 using, for example, the triangulation principle,based on the signal intensity information received from the wirelessterminal 40 and on the above-described base station information. Theposition estimation server 20 notifies the wireless terminal 40 ofposition information indicating the above-described estimated position.The wireless terminal 40 can thereby recognize the position informationof the terminal itself. Note that the position estimation server 20 canrespond to a position estimation request not only from the wirelessterminal 40 but also from a plurality of other wireless terminals.

In this manner, according to the present embodiment, the wirelessterminal 40 performs signal intensity measurement of the wireless signaltransmitted from the surrounding base station 30, and transmits ameasurement result to the position estimation server 20. Thus, it ispossible to acquire the position information of the terminal itself.

Background of Present Embodiment

Here, the position information may be information indicating atwo-dimensional position, such as the latitude and longitude, that doesnot include a height direction. Accordingly, the wireless terminal 40existing in a certain building or structure can acquire, from theposition estimation server 20, position information of the building orstructure, or the name of the building or structure when the positioninformation and the name of the building or structure are associated andstored in the position estimation server 20.

However, if not only the name of the building or structure in which thewireless terminal 40 exists, but also which section in the building orstructure the wireless terminal 40 exists is ascertained by the wirelessterminal 40, the wireless terminal 40 can provide a user with guidancein accordance with a floor, for example. Therefore, causing the wirelessterminal 40 to ascertain floor information indicating the floor of thebuilding or structure is practically important.

In order to acquire the floor information, a technology that uses GPS,for example, is conceivable. However, since it is difficult for anavigation message from a GPS satellite to reach indoor or undergroundlocations, the use of the GPS in a building or structure is difficult.In addition, even if an altitude (above sea level) of a receiver can bemeasured by the GPS, it is necessary to ensure that:

(1) a relationship between the altitude and each floor of each buildingor structure is stored in a database; and

(2) an estimated error of the altitude is sufficiently smaller than theheight of each floor (for example, approximately 1 m).

To address this, in light of the foregoing circumstances, the positionestimation system 1 according to the present embodiment has beencreated. With the position estimation system 1 according to the presentembodiment, it is possible to estimate the position of the wirelessterminal 40 in a building or structure, while simplifying a troublesomeoperation of pre-registration. Hereinafter, the position estimationsystem 1 according to the present embodiment will be described indetail.

[2] DETAILED EXPLANATION OF POSITION ESTIMATION SYSTEM ACCORDING TOPRESENT EMBODIMENT

The present embodiment is roughly classified into: a registration stagein which the position estimation server 20 registers the base stationinformation including the floor information; and an estimation stage inwhich the position estimation server 20 estimates the floor informationof the wireless terminal 40 based on the registered base stationinformation. Therefore, in the description below, after explaining ahardware configuration of the position estimation server 20 included inthe position estimation system 1 according to the present embodiment,the registration stage and the estimation stage of the floor informationwill be specifically explained.

[2-1] Hardware Configuration of Position Estimation Server

FIG. 2 is a block diagram showing a hardware configuration of theposition estimation server 20. The position estimation server 20 isprovided with a central processing unit (CPU) 201, a read only memory(ROM) 202, a random access memory (RAM) 203, a host bus 204, a bridge205, an external bus 206, an interface 207, an input device 208, anoutput device 210, a storage device (HDD) 211, a drive 212 and acommunication device 215.

The CPU 201 functions as an arithmetic processing device and a controldevice, and controls an overall operation within the position estimationserver 20 in accordance with various programs. Further, the CPU 201 maybe a microprocessor. The ROM 202 stores programs, operation parametersand the like that are used by the CPU 201. The RAM 203 temporarilystores programs that are used in execution by the CPU 201, parametersthat appropriately change in the execution, and the like. These aremutually connected by the host bus 204 that is formed of a CPU bus andthe like.

The host bus 204 is connected, via the bridge 205, to the external bus206, which is, for example, a peripheral componentinterconnect/interface (PCI) bus. Note that the host bus 204, the bridge205 and the external bus 206 need not necessarily be formed separately,and these functions may be implemented on a single bus.

The input device 208 is formed by input means for inputting informationby the user, an input control circuit and the like. Examples of theinput means include a mouse, a keyboard, a touch panel, a button, amicrophone, a switch, a lever and the like. The input control circuitgenerates an input signal based on input by the user, and outputs it tothe CPU 201. By operating the input device 208, an administrator of theposition estimation server 20 can input various types of data to theposition estimation server 20 or give an instruction of a processingoperation.

The output device 210 includes, for example, a display device such as acathode ray tube (CRT) display device, a liquid crystal display (LCD)device, or an organic light emitting display (OLED) device and a lamp,and an audio output device such as a speaker and a headphone. The outputdevice 210 outputs played back content, for example. More specifically,the display device displays, as text or images, various types ofinformation such as played back video data. On the other hand, the audiooutput device converts the played back audio data etc. to audio andoutputs it.

The storage device 211 is a device for storing data, and is structuredas an example of a storage portion of the position estimation server 20according to the present embodiment. The storage device 211 may includea storage medium, a recording device that records data in the storagemedium, a read-out device that reads out data from the storage medium, adeletion device that deletes the data recorded in the storage medium,and the like. The storage device 211 is formed by a hard disk drive(HDD), for example. The storage device 211 drives a hard disk and storesprograms executed by the CPU 201 and various types of data. Further, thebase station information to be described later is recorded in thestorage device 211.

The drive 212 is a reader/writer for the storage medium, and isincorporated in or externally attached to the position estimation server20. The drive 212 reads out information recorded in an attached magneticdisk, optical disk or magneto optical disk, or in a removable storagemedium 24 such as a semiconductor memory, and outputs the information tothe RAM 203.

The communication device 215 is a communication interface that is formedby a communication device etc. to connect with the communication network12, for example. Further, the communication device 215 may be a wirelesslocal area network (LAN) compatible communication device, a wireless USBcompatible communication device, or a wired communication device thatperforms communication by wire. The communication device 215 transmitsand receives various types of information, such as signal intensityinformation, floor information, position information and the like, toand from the wireless terminal 40 via the communication network 12.

Note that the hardware configuration of the position estimation server20 is described above with reference to FIG. 2. Hardware of the wirelessterminal 40 can be configured to be substantially the same as that ofthe position estimation server 20, and an explanation thereof istherefore omitted.

[2-2] Registration of Floor Information

Next, registration of the floor information in the position estimationsystem 1 according to the present embodiment will be described withreference to FIG. 3 to FIG. 8.

FIG. 3 is a function block diagram showing the configurations of theposition estimation server 20 and the wireless terminal 40 that areincluded in the position estimation system 1 according to the presentembodiment. As shown in FIG. 3, the position estimation server 20 isprovided with a communication portion 216, a base station informationmanagement portion 220, a storage portion 224, and a positioninformation estimation portion 238 that includes a retrieval portion232, a distance evaluation portion 234, a floor estimation portion 236and a position information estimation portion 238. Further, the wirelessterminal 40 is provided with a communication portion 416, a measurementportion 420, a display screen generation portion 424, a display portion428, an operation portion 432, a registration request portion 436 and aninformation acquisition portion 440.

The communication portion 416 of the wireless terminal 40 is aninterface with the base station 30 or the position estimation server 20,and has a function as a transmitting portion and a receiving portion fortransmitting and receiving various types of information to and from thebase station 30 or the position estimation server 20. For example, thecommunication portion 416 receives, from the base station 30, a wirelesssignal including the base station ID of the base station 30. Further,the communication portion 416 transmits, to the position estimationserver 20, registration request information that will be describedlater.

Note that the communication portion 416 may have a wirelesscommunication function that is defined by Institute of Electrical andElectronic Engineers (IEEE) 802. 11a, b, g, and the like. Further, thecommunication portion 416 may have a multiple input multiple output(MIMO) communication function that is defined by IEEE 802. 11n.Furthermore, the communication portion 416 may have a communicationfunction that corresponds to Worldwide Interoperability for MicrowaveAccess (WiMAX) planned by IEEE802. 16.

The measurement portion 420 measures a signal intensity of a wirelesssignal received by the communication portion 416 from the base station30. For example, the measurement portion 420 acquires signal intensityinformation shown in FIG. 5, by performing signal intensity measurementat a position P1 shown in FIG. 4.

FIG. 4 is an explanatory diagram schematically showing a cross sectionof a certain building or structure. More specifically, FIG. 4 shows thecross section of a 6-story building or structure, and the base station30 is installed on each floor of the building or structure. For example,the base station 30A is installed on the 1st floor of the building orstructure, the base station 30B is installed on the 2nd floor, the basestation 30C is installed on the 3rd floor, the base station 30D isinstalled on the 4th floor, the base stations 30E and 30F are installedon the 5th floor, and the base station 30G is installed on the 6thfloor, 2nd floor.

FIG. 5 is an explanatory diagram showing an example of signal intensityinformation that is acquired by signal intensity measurement at theposition P1. Note that, in this specification, for convenience ofexplanation, the base station ID is the same as the reference numeral ofeach of the base stations 30. For example, in this specification, it isassumed that the base station ID of the base station 30A shown in FIG. 4is 30A.

As shown in FIG. 4, the base station 30D is installed on the 4th floorthat is the same floor as the position P1, and the base station 30C isinstalled on the 3rd floor that is the floor below the position P1. Thebase stations 30E and 30F are installed on the 5th floor that is thefloor above the position P1, and the base station 30G is installed onthe 6th floor. Here, the signal intensity of the wireless signaltransmitted from each of the base stations 30 is attenuated as thedistance becomes greater. Further, in a case where there is an obstacle,such as a wall, a floor or a ceiling, between the wireless terminal 40and each of the base stations 30, the signal intensity of the wirelesssignal transmitted from each of the base stations 30 deterioratesbecause the wireless signal reaches the wireless terminal 40 after beingdiffracted by the obstacle or partially passing through the obstacle.

More specifically, as shown in FIG. 5, the signal intensity of thewireless signal transmitted from the base station 30D, which isinstalled on the 4th floor that is the same floor as the position P1 atwhich the wireless terminal 40 exists, is “−57 dBm,” which is a highestvalue. Meanwhile, the signal intensity of the wireless signaltransmitted from the base station 30C, which is provided via the floorwith respect to the position P1 at which the wireless terminal 40exists, is “−67 dBm”, and the signal intensity is lower compared to thewireless signal transmitted from the base station 30D. In a similarmanner, the signal intensities at the position P1 of the base stations30E, 30F and 300, which are provided via an obstacle with respect to theposition P1, are lower compared to the wireless signal transmitted fromthe base station 30D.

Here, the configuration of the wireless terminal 40 will be describedagain with reference to FIG. 3. The display screen generation portion424 generates various types of display screens, and causes the displayportion 428 to display the generated display screens. For example, thedisplay screen generation portion 424 generates a floor informationregistration screen and a guidance screen etc. that corresponds to floorinformation acquired by the information acquisition portion 440. Thedisplay portion 428 corresponds to the output device 210, which has beenexplained with reference to FIG. 2, and displays the various types ofdisplay screens generated by the display screen generation portion 424.Hereinafter, a specific example of the floor information registrationscreen that is generated by the display screen generation portion 424and is displayed on the display portion 428 will be described withreference to FIG. 6.

FIG. 6 is an explanatory diagram showing an example of the floorinformation registration screen that is generated by the display screengeneration portion 424. The floor information registration screen is ascreen to register, in the position estimation server 20, the floorinformation of each of the base stations 30 that is used at the time offloor estimation of the wireless terminal 40, and it is generated basedon a user operation, for example.

More specifically, as shown in FIG. 6, the floor informationregistration screen includes a floor input area 52, a building/structurename input area 54, and an OK button 56. The floor input area 52 is anarea to input the floor (level) on which the wireless terminal 40currently exists. The user of the wireless terminal 40 can input thefloor to the floor input area 52 by operating the operation portion 432.Note that, in FIG. 6, a case is assumed in which the user at theposition P1 registers floor information. Therefore, an example is shownin which “4th floor” is input to the floor name input area 52.

The building/structure name input area 54 is an area to input the nameof the building or structure in which the wireless terminal 40 currentlyexists. The user of the wireless terminal 40 can input the name of thebuilding or structure to the building/structure name input area 54 byoperating the operation portion 432. Note that, in FIG. 6, a case isshown in which “KK building” is input to the building/structure nameinput area 54. The OK button 56 is a button to confirm the content inputto the floor input area 52 and the building/structure name input area54.

Note that, in the above description, the floor information is used as anexample of section information that indicates a section of the buildingor structure. However, the section information is not limited to thisexample. For example, the section information may be information thatshows the name of a room (room 301, conference room, reception room orthe like) that is defined by an obstacle, such as a wall, even if beingon the same floor, or may be a user organization (SSS Co., Ltd., TTdivision, UUU store). Further, although the building is used as anexample of the building or structure in the above description, thebuilding or structure is not limited to this example. For example, thebuilding or structure may be a subway station yard, an attractionfacility (in this case, a haunted house, a cafeteria, a VVV area and thelike are assumed as the section information), a Shinkansen train (inthis case, a carriage number is assumed as the section information), ora given man-made object such as a ship.

The operation portion 432 is an interface for the user to input varioustypes of information or various types of instructions to the wirelessterminal 40. As described above, the user can cause the display screengeneration portion 424 to generate the floor information registrationscreen by operating the operation portion 432, and can input floorinformation, such as the floor name and the building/structure name, onthe floor information registration screen.

When the OK button 56 is selected by the user on the floor informationregistration screen, the registration request portion 436 transmits theregistration request information input onto the floor informationregistration screen, including the floor name, the name of the buildingor structure, and the signal intensity information, to the positionestimation server 20 via the communication portion 416. FIG. 7A shows aspecific example of the registration request information.

FIG. 7A is an explanatory diagram showing a specific example of theregistration request information that is transmitted from the mobileterminal 40 at the position P1. As shown in FIG. 7A, the registrationrequest portion 436 associates the signal intensity information (firstmeasurement information) acquired by the measurement portion 420 at theposition P1 with the floor information of “KK building” and “4th floor”,and transmits the associated information to the position estimationserver 20 as the registration request information. Note that themeasurement portion 420 may use the selection of the OK button 56 by theuser on the floor information registration screen as a trigger toperform signal intensity measurement.

FIG. 7B, FIG. 7C and FIG. 7D show specific examples of registrationrequest information, similarly to FIG. 7A. More specifically, FIG. 7B isan explanatory diagram showing a specific example of registrationrequest information that is transmitted from the mobile terminal 40 at aposition P2. FIG. 7C is an explanatory diagram showing a specificexample of registration request information that is transmitted from themobile terminal 40 at a position P3. Further, FIG. 7D is an explanatorydiagram showing a specific example of registration request informationthat is transmitted from the mobile terminal 40 at a position P4.

When referring to FIG. 7A to FIG. 7D, it can be confirmed that, evenwhen wireless signals are transmitted from the same base station 30,signal intensities are different from each other depending on whetherbeing on the same floor and on a distance from each position. Note that,in the above description, an example is described in which theregistration request information includes signal intensity informationas an example of measurement information. However, the presentembodiment is not limited to this example. For example, instead of thesignal intensity information, the registration request information mayinclude distance information between the acquisition position of thesignal intensity information and each of the base stations 30, thedistance information being estimated from the signal intensityinformation by a method described later.

Here, FIG. 3 will be explained again. The communication portion 216 ofthe position estimation server 20 is an interface with the wirelessterminal 40, and has a function as a transmitting portion and areceiving portion for transmitting and receiving various types ofinformation to and from the wireless terminal 40. For example, thecommunication portion 216 receives from the wireless terminal 40 theregistration request information shown in the group of FIG. 7.

The base station information management portion 220 performs managementof base station information, such as registration of new base stationinformation into the storage portion 224, and update, modification anddeletion etc. of the base station information registered in the storageportion 224. It should be noted herein that the base station informationis information that includes, for each of the base stations 30, a basestation ID, position information (the latitude and longitude) indicatingthe position at which the base station is installed, signal intensityand floor information.

Note that, instead of signal intensity, the base station information mayinclude a virtual distance between a signal intensity acquisitionposition and an installation position of the base station 30, thevirtual distance being estimated from signal intensity. The virtualdistance between the signal intensity acquisition position and theinstallation position of the base station 30 can be estimated by, forexample, substituting signal intensity into Expression 1 below.

[Expression 1]

Estimated distance=10^(((-A-rssi)/B))  (Expression 1)

In Expression 1, A and B are constants, and rssi indicates signalintensity. For example, when A=32, B=25 and signal intensity=−80 dBm,the estimated virtual distance between the signal intensity acquisitionposition and the installation position of the base station 30 can becalculated to be 83 m. The signal intensity significantly depends onwhether or not there is an obstacle, and the estimated distancecalculated by the above Expression 1 does not necessarily coincide withan actual distance. However, the estimated distance calculated by theabove Expression 1 serves as an index indicating a condition of acommunication path between the signal intensity acquisition position andthe installation position of the base station 30.

For example, it can be evaluated that, as the estimated distancecalculated by the above Expression 1 is smaller, the communication pathbetween the signal intensity acquisition position and the installationposition of the base station 30 is in a better condition, and as theestimated distance calculated by the above Expression 1 is greater, thecommunication path between the signal intensity acquisition position andthe installation position of the base station 30 is in a worsecondition. Note that, for convenience of explanation, in the descriptionbelow, it is assumed that the base station information includes, insteadof signal intensity, the estimated distance that is calculated by theabove Expression 1.

When the communication portion 216 receives registration requestinformation from the wireless terminal 40, the base station informationmanagement portion 220 performs addition, update or the like of the basestation information in the storage portion 224, based on theregistration request information. For example, when the registrationrequest information shown in the group of FIG. 7 is received from one ormore wireless terminals 40, the base station information managementportion 220 registers a set of base station information shown in FIG. 8in the storage portion 224.

FIG. 8 is an explanatory diagram showing a specific example of the setof base station information that is registered in the storage portion224. As shown in FIG. 8, the base station ID, the estimated distance andthe floor information are associated with each other in each piece ofbase station information. For example, the base station informationindicating the base station ID “30C”, the estimated distance “83 m” andthe floor information “5th floor” is base station information that isregistered based on the registration request information at the positionP2 shown in FIG. 7B. More specifically, this piece of base stationinformation indicates that signal intensity measurement was performed ata position where the distance from the base station 30C was estimated tobe 83 m, and that the measurement floor was “5th floor”.

Note that, as shown in FIG. 4, in actuality, the base station 30C isinstalled on the 3rd floor. That is, in the present embodiment, thefloor information registered as the base station information is notnecessarily completely accurate. However, according to the presentembodiment, even when inaccurate floor information is included, it ispossible to appropriately estimate the floor on which the wirelessterminal 40 exists, as will be described in “[2-3] Estimation of floorinformation”.

On the other hand, a method is also conceivable in which each of thebase stations 30 are visually confirmed, accurate floor information ofeach of the installed base stations 30 is registered in the positionestimation server 20, and a current floor is estimated based on theregistered floor information. However, it is troublesome to visuallyconfirm each of the base stations 30. In addition, there is a case inwhich each of the base stations 30 is installed in a location thatcannot be visually confirmed. In comparison to this, the positionestimation system 1 according to the present embodiment is effective inthat information necessary to estimate the current floor can beregistered without visually confirming each of the base stations 30.

Note that the storage portion 224 that stores the base stationinformation shown as an example in FIG. 8 may be a storage medium suchas, for example, a non-volatile memory such as an electrically erasableprogrammable read-only memory (EEPROM), an erasable programmableread-only memory (EPROM), or the like, a magnetic disk such as a harddisk, a magnetic material disc, or the like, an optical disk such as acompact disc recordable (CD-R), a compact disc rewritable (CD-RW), adigital versatile disc recordable (DVD-R), a digital versatile discrewritable (DVD-RW), a dual-layer digital versatile disc recordable(DVD+R), a dual-layer digital versatile disc rewritable (DVD+RW), adigital versatile disc random access memory (DVD-RAM), a Blu-ray™ discrecordable (BD-R), a Blu-ray™ disc rewritable (BD-RE), or the like, or amagneto-optical (MO) disk. Further, although the base stationinformation includes the position information indicating the latitudeand longitude of each of the base stations 30, a description of theposition information is omitted in FIG. 8. Further, although the floorinformation can include not only the floor name but also the name of thebuilding or structure, such as KK building, a description about the nameof the building or structure is omitted below.

[2-3] Estimation of Floor Information

Next, with reference to FIG. 3 and FIG. 9 to FIG. 11, estimation offloor information in the position estimation system 1 according to thepresent embodiment will be described.

In order to estimate a current floor of the wireless terminal 40, theposition estimation server 20 uses the signal intensity information inthe wireless terminal 40, and the base station information registered inthe storage portion 224 that is described in “[2-2] Registration offloor information”.

For this reason, the information acquisition portion 440 of the wirelessterminal 40 transmits, as a floor information estimation request,measurement information (second measurement information) acquired bysignal intensity measurement in the measurement portion 420, to theposition estimation server 20 via the communication portion 416. Theinformation acquisition portion 440 may periodically transmit themeasurement information of the floor information, or may transmit itbased on a user operation on the operation portion 432. Hereinafter,processing when the information acquisition portion 440 of the wirelessterminal 40 at a position P5 shown in FIG. 4 transmits the measurementinformation will be described as a specific example. Note that signalintensity information could be used as the measurement information.However, as shown in FIG. 9, the measurement information may beinformation in which the base station ID is associated with the distancebetween the measurement position and each of the base stations 30, thedistance being estimated from the signal intensity information.

FIG. 9 is an explanatory diagram showing a specific example ofmeasurement information that is transmitted from the informationacquisition portion 440 at the position P5 shown in FIG. 4. As shown inFIG. 4, the position P5 is located on the 4th floor. Therefore, it maybe considered that an estimated distance from the base station 30Dinstalled on the same 4th floor is shortest. However, a case is alsoassumed in which an estimated distance from the base station 30Einstalled on the upper 5th floor is shorter than the estimated distancefrom the base station 30D installed on the same 4th floor, as shown inFIG. 9. This occurs when the degree of attenuation of the signalintensity of a wireless signal is low between the base station 30E andthe position P5, due to a ceiling material, whether or not there is astairwell, and the like, although the position P5 and the base station30E are located on different floors.

Therefore, even if accurate floor information is registered in advancein each of the base stations 30 through complicated processing, whenusing a method that simply estimates floor information based on the basestation 30 with the strongest signal intensity, it is predicted thatfloor information different from actual floor information is likely tobe estimated. In comparison to this, with the position estimation server20 according to the present embodiment, it is possible to estimate thecurrent floor with high accuracy, even when the signal intensity of thebase station 30 installed on a different floor from the measurementposition is strongest and the estimated distance is shortest.Hereinafter, the position estimation server 20 that achieves such afunction will be described in detail.

When the communication portion 216 receives measurement information as afloor information estimation request, the retrieval portion 232 of theposition estimation server 20 extracts the base station ID included inthe measurement information, and retrieves the base station informationthat is associated with the extracted base station ID from the storageportion 224.

The distance evaluation portion 234 evaluates a relationship between acurrent position and a registration position of the base stationinformation, based on the measurement information received by thecommunication portion 216 and the base station information retrieved bythe retrieval portion 232. A specific example of an evaluation method bythe distance evaluation portion 234 will be described with reference toFIG. 10.

FIG. 10 is an explanatory diagram showing a specific example of theevaluation method by the distance evaluation portion 234. As shown inFIG. 10, an estimated distance (a second distance) between a currentposition and a base station 30 i (i is a given capital alphabeticcharacter) is expressed as d (30 i), the estimated distance beingincluded in the measurement information received by the communicationportion 216. Further, an estimated distance (a first distance) between aregistration position Pj (j is a given number) and the base station 30 iis expressed as d (30 i, Pj), the estimated distance being included inthe base station information retrieved by the retrieval portion 232.Note that, when the measurement information or the base stationinformation includes signal intensity information instead of theestimated distance, the distance evaluation portion 234 may convert thesignal intensity information to the estimated distance according toExpression 1. The distance evaluation portion 234 performs calculationof Expression 2 below that is represented using the above-describedexpressions.

[Expression 2]

D(30i,Pj)=d(30i)+d(30i,Pj)  (Expression 2)

Further, FIG. 11 shows specific examples of D(30 i, Pj) that areobtained by the calculation shown by the above Expression 2.

FIG. 11 is an explanatory diagram showing specific examples of distanceevaluation performed by the distance evaluation portion 234. As shown byExpression 2 and in FIG. 11, the distance evaluation portion 234calculates D(30 i, Pj) by adding d(30 i) and d(30 i, Pj) that relate tothe same base station. For example, the distance evaluation portion 234calculates a value of D(30C, P1) to be 55 m, by adding 30 m that is avalue of d(30C) and 25 m that is a value of d(30C, P1).

It should be noted herein that, when a registration position Px and thecurrent position are located on the same floor and a base station 30 yis installed on the floor, a value of D(30 y, Px) becomes relativelysmall. This is because an estimated distance between the registrationposition Px and the base station 30 y, and an estimated distance betweenthe current position and the base station 30 y become smaller.

On the other hand, when a registration position Pv and the currentposition are located on different floors and a base station 30 w isinstalled on the same floor as either the registration position Pv orthe current position, it is predicted that D(30 w, Pv) is larger thanD(30 y, Px). This is because, since the base station 30 w is installedon a different floor from the registration position Pv or the currentposition, an estimated distance between the registration position Pv andthe base station 30 w, or an estimated distance between the currentposition and the base station 30 w becomes larger.

From this point of view, the floor estimation portion 236 has a functionas a selection portion that selects D(30 imin, Pjmin) that has thesmallest value among D(30 i, Pj) obtained by the distance evaluationportion 234. Then, the floor estimation portion 236 estimates that thefloor information registered at Pjmin is the current floor information.

More specifically, the floor estimation portion 236 selects D(30D, P1)(29 m) that has the smallest value among D(30 i, Pj) shown in FIG. 11.Then, the floor estimation portion 236 estimates that the current floorinformation is “4th floor” that is registered at the position P1. Here,the current position is the position P5 on the 4th floor. Therefore, itcan be confirmed that, according to the present embodiment, the currentfloor information can be estimated with high accuracy.

Here, the configuration of the position estimation server 20 will bedescribed again with reference to FIG. 3. When the communication portion216 receives measurement information from the wireless terminal 40, theposition information estimation portion 238 estimates the positioninformation indicating the latitude and longitude of the wirelessterminal 40. For example, the position estimation portion 238 uses themeasurement information received by the communication portion 216 andthe base station information registered in the storage portion 224 toestimate a current position O of the wireless terminal 40 in accordancewith Expressions 3 to 5 described below.

$\begin{matrix}\left\lbrack {{Expression}\mspace{14mu} 3} \right\rbrack & \; \\{O = {\frac{1}{W} \cdot {\sum\limits_{i}\left( {{Wi} \cdot {Ai}} \right)}}} & \left( {{Expression}\mspace{14mu} 3} \right) \\\left\lbrack {{Expression}\mspace{14mu} 4} \right\rbrack & \; \\{{Wi} = \frac{1}{d\left( {30i} \right)}} & \left( {{Expression}\mspace{14mu} 4} \right) \\\left\lbrack {{Expression}\mspace{14mu} 5} \right\rbrack & \; \\{W = {\sum\limits_{i}{Wi}}} & \left( {{Expression}\mspace{14mu} 5} \right)\end{matrix}$

In Expression 3, Ai indicates position information of an i-th basestation registered in the storage portion 224. Therefore, when theposition information is shown by the latitude and longitude, Expression3 is applied separately to the latitude and longitude. Further, as shownin Expression 4, Wi is a weighting factor that is obtained based on theestimated distance d(30 i) between the wireless terminal 40 and the basestation 30 i, which is estimated from signal intensity. Further, W is asum of weighting factors as shown in Expression 5.

Referring to Expression 3, position information of the base stationwhose d(30 i) is small is significantly reflected on the currentposition O of the wireless terminal 40. On the other hand, positioninformation of the base station whose d(30 i) is large has a smallinfluence on the current position O of the wireless terminal 40. Theposition estimation portion 238 can rationally estimate the currentposition O of the wireless terminal 40 by using Expression 3 describedabove.

Note that a position estimation method of the wireless terminal 40 isnot limited to the method that uses the above-described Expression 3.For example, the position of the base station that is a transmissionsource of a signal with the highest signal intensity among signalsreceived by the wireless terminal 40 may be estimated as the position ofthe wireless terminal 40. Alternatively, a position that is the centerof the base stations that are transmission sources of signals with asignal intensity equal to or more than a predetermined threshold valuethat are received by the wireless terminal 40 may be estimated as theposition of the wireless terminal 40.

The floor information estimated by the floor estimation portion 236 inthe above-described manner, and the position information estimated bythe position estimation portion 238 are notified from the communicationportion 216 to the wireless terminal 40. Then, for example, the displayscreen generation portion 424 of the wireless terminal 40 generates adisplay screen based on the floor information and the positioninformation notified from the position estimation server 20. By doingthis, it possible to supply information that corresponds to the floorinformation and the position information to the user of the wirelessterminal 40.

Note that, when the measurement information received by thecommunication portion 216 includes a base station ID whose positioninformation is unknown, the base station management portion 220 mayregister, as the position information of the base station ID, thecurrent position O that is estimated from the measurement information bythe position information estimation portion 238. In a similar manner,when the registration request information received by the communicationportion 216 includes a base station ID whose position information isunknown, the base station management portion 220 may register, as theposition information of the base station ID, the current position O thatis estimated from the registration request information by the positioninformation estimation portion 238. With the above-describedconfiguration, it is possible to automatically enhance the positioninformation of the base station 30 that is maintained in the positionestimation server 20.

Modified Examples

In the above description, an example is explained in which the floorestimation portion 236 performs floor estimation based on the value ofD(30 i, Pj) obtained by the distance evaluation portion 234. However,the present invention is not limited to this example. For example, thedistance evaluation portion 234 may calculate an average of sum valuesof an estimated distance included in the measurement information, andestimated distances which are associated with the same base station IDamong the pieces of base station information retrieved by the retrievalportion 232 and which are also associated with the same floorinformation. Then, the floor estimation portion 236 may select floorinformation by extracting a minimum value from among D(30 i, Pj)obtained by the distance evaluation portion 234, or from among averagevalues.

For example, in FIG. 8, there are a plurality of estimated distances (10m, 13 m) that are associated with the same base station ID “30D” andwith the same floor information “4th floor”. Here, if the estimateddistance between the current position and the base station 30D that isobtained from the measurement information is 19 m, the distanceevaluation portion 234 calculates an average value of 30.5 m that isrepresented by the expression ((10+19)+(13+19))/2.

When the above-described average value 30.5 m is the minimum value amongD(30 i, Pj) obtained by the distance evaluation portion 234, or amongthe average values, the floor estimation portion 236 selects the floorinformation “4th floor” that corresponds to the estimated distances (10m, 13 m) used in the calculation of the average value.

With the above-described configuration, even if erroneous base stationinformation is accidentally registered in the storage portion 224, it ispossible to reduce the degree of adverse effects on floor estimationcaused by the base station information, and to secure accuracy of floorestimation.

Further, the distance evaluation portion 234 may have a function as apriority processing portion that performs processing such that, as thenumber of pieces of the same floor information associated with the samebase station ID becomes larger, the corresponding floor information isselected with priority by the floor estimation portion 236. For example,as the number of pieces of the same floor information associated withthe same base station ID becomes larger, the distance evaluation portion234 may treat, as d(30 i, Pj), a distance that is shorter than theestimated distance associated with the corresponding floor information.

[3] OPERATION OF POSITION ESTIMATION SYSTEM ACCORDING TO PRESENTEMBODIMENT

The functions of the position estimation system 1 according to thepresent embodiment are described above with reference to FIG. 3 to FIG.11. Next, an operation of the position estimation system 1 according tothe present embodiment will be described with reference to FIG. 12 andFIG. 13.

FIG. 12 is a sequence diagram showing an operation flow of the positionestimation system 1 according to the present embodiment. As shown inFIG. 12, first, the measurement portion 420 of a wireless terminal 40Aperforms signal intensity measurement on a certain floor of a buildingor structure (S302), and the user inputs a current floor on the floorinformation registration screen by operating the operation portion 432(S304).

Following this, the registration request portion 436 of the wirelessterminal 40A transmits, to the position estimation server 20,registration request information that includes measurement information,such as signal intensity information acquired by signal intensitymeasurement or estimated distance information, and floor informationinput by the user (S306). When the communication portion 216 receivesthe registration request information, the base station informationmanagement portion 220 of the position estimation server 40 associatesthe measurement information with the floor information included in theregistration request information, and registers the associatedinformation in the storage portion 224 as the base station information(S308).

In a similar manner, the measurement portion 420 of a wireless terminal40B performs signal intensity measurement on a certain floor of thebuilding or structure (S312), and a user inputs a current floor on thefloor information registration screen by operating the operation portion432 (S314).

Next, the registration request portion 436 of the wireless terminal 40Btransmits, to the position estimation server 20, registration requestinformation that includes measurement information, such as signalintensity information acquired by signal intensity measurement orestimated distance information, and floor information input by the user(S316). When the communication portion 216 receives the registrationrequest information, the base station information management portion 220of the position estimation server 40 associates the measurementinformation with the floor information included in the registrationrequest information, and registers the associated information in thestorage portion 224 as the base station information (S318). In thismanner, the base station information including the floor information isaccumulated in the storage portion 224 of the position estimation server20.

After that, the measurement portion 420 of a wireless terminal 40Fperforms signal intensity measurement of the wireless signal transmittedfrom the surrounding base station 30 (S322), and the informationacquisition portion 440 transmits the measurement information acquiredby the signal intensity measurement to the position estimation server 20(S324). When the communication portion 216 receives the measurementinformation, the position estimation server 20 estimates positioninformation and floor information of the wireless terminal 40F, based onthe measurement information and the base station information registeredin the storage portion 224 (S326), and transmits them to the wirelessterminal 40F (S328).

FIG. 13 is a flow chart showing a detailed flow of estimation processingthat is performed by the position estimation server 20. As shown in FIG.13, first, when the communication portion 216 receives measurementinformation from the wireless terminal 40 (S342), the retrieval portion232 retrieves base station information including the base station IDthat is contained in the measurement information, from the storageportion 224 (S344).

After that, the distance evaluation portion 234 evaluates the distancebetween the registration position of the base station information thatis retrieved by the retrieval portion 232 and the current wirelessterminal 40 by calculation, using the method described in “[2-3]Estimation of floor information”, for example (S346). More specifically,the distance evaluation portion 234 calculates D(30 i, Pj) in accordancewith Expression 2. Then, the floor estimation portion 236 selects floorinformation based on an evaluation result by the distance evaluationportion 234 (S348).

Further, the distance estimation portion 238 estimates the positioninformation indicating the latitude and longitude of the wirelessterminal 40 in accordance with, for example, Expression 3, using themeasurement information received by the communication portion 216 andthe base station information registered in the storage portion 224.Then, the communication portion 216 transmits, to the portable terminal40, the floor information estimated by the floor estimation portion 236and the position information estimated by the position informationestimation portion 238 (S352).

[4] CONCLUSION

As described above, according to the present embodiment, the positionestimation server 20 can accurately estimate the floor of the wirelessterminal 40, based on the measurement information acquired by signalintensity measurement in the wireless terminal 40 and the base stationinformation registered in the storage portion 224 of the positionestimation server 20. It should be noted herein that the base stationinformation registered in the storage portion 224 is information inwhich the floor information indicating the floor where signal intensitymeasurement has been performed in advance by a given wireless terminal40 is associated with the measurement information that was acquired bythe signal intensity measurement. Therefore, the present embodiment isespecially effective in that the floor of the wireless terminal 40 canbe accurately estimated in addition to the position information, whileeliminating the troublesome operation of visually confirming each of thebase stations 30 in advance and registering the base station informationof each of the base stations 30. Moreover, the present embodiment isalso advantageous in that there is no need to provide the wirelessterminal 40 with a special sensor for floor estimation.

The preferred embodiments of the present invention have been describedabove with reference to the accompanying drawings, whilst the presentinvention is not limited to the above examples, of course. A personskilled in the art may find various alternations and modificationswithin the scope of the appended claims, and it should be understoodthat they will naturally come under the technical scope of the presentinvention.

For example, in the above-described embodiment, an example is describedin which a plurality of estimated positions that are associated with thesame base station ID and the same floor information can exist in thestorage portion 224. However, the present invention is not limited tothis example. As another embodiment, the base station informationmanagement portion 220 may cause a certain base station ID and certainfloor information to be associated only with the shortest estimateddistance. In the example shown in FIG. 8, the base station managementportion 220 may delete the information of the base station ID “30C”, thefloor information “4th floor”, and the estimated distance “28 m”, forexample. Alternatively, when the information of the base station ID“30C”, the floor information “4th floor”, and the estimated distance “25m” has already been registered, the base station information managementportion 220 may not register the information of the base station ID“30C”, the floor information “4th floor”, and the estimated distance “28m”

Further, in the above-described embodiment, an example is described inwhich the floor information is estimated by converting the signalintensity information to an estimated distance in accordance withExpression 1. However, the present invention is not limited to thisexample. In other words, the present invention can be achieved using aparameter of a given dimension that is acquired by signal intensitymeasurement.

Furthermore, each step of the processing performed by the positionestimation system 1 or the position estimation server 20 in thisspecification does not have to be performed in time series in line withthe order detailed in the sequence diagram or the flow chart. Forexample, each step of the processing performed by the positionestimation system 1 or the position estimation server 20 may includeprocessing that is performed in parallel or individually (for example,parallel processing or object oriented processing).

Note that, a computer program can also be created that causes hardwaresuch as the CPU 201, the ROM, 202 and the RAM 203 that are built-in tothe position estimation server 20 and the portable terminal 40 toperform functions that are the same as each structural element of theabove-described position estimation server 20 and the portable terminal40. Further, a storage medium that stores the computer program is alsoprovided. Moreover, if each function block shown by the functional blockdiagram in FIG. 3 is structured by hardware, a series of processes canbe realized by hardware.

1. A wireless terminal comprising: a wireless signal receiving portionthat receives a wireless signal transmitted from a base station; ameasurement portion that performs signal intensity measurement of thewireless signal received by the wireless signal receiving portion; andan information transmitting portion that transmits at least one piece ofsecond measurement information acquired by the signal intensitymeasurement of the wireless signal performed by the measurement portion,and at least one piece of base station identification information thatindicates a base station of a transmission source of the wireless signaland that is associated with each of the at least one piece of secondmeasurement information.
 2. A wireless terminal comprising: a wirelesssignal receiving portion that receives a wireless signal transmittedfrom a base station; a measurement portion that performs signalintensity measurement of the wireless signal received by the wirelesssignal receiving portion; an input portion to which section informationindicating one section of a building structure is input by a user; andan information transmitting portion that transmits at least one piece ofsecond measurement information acquired by the signal intensitymeasurement of the wireless signal performed by the measurement portion,and at least one piece of base station identification information thatindicates a base station of a transmission source of the wireless signaland that is associated with each of the at least one piece of secondmeasurement information.
 3. A wireless terminal comprising: acommunication portion for receiving from a base station, a wirelesssignal comprising base station identification information of the basestation, and for transmitting information comprising registrationrequest information to a position estimation server; a measurementportion for performing a signal intensity measurement of the wirelesssignal received by the communication portion; an information acquisitionportion for acquiring and transmitting to the position estimation servervia the communication portion, at least one piece of second measurementinformation acquired by the signal intensity measurement of the wirelesssignal performed by the measurement portion; a display screen generationportion for generating one or more display screens; a display portionfor displaying the one or more display screens generated by the displayscreen generation portion; an operation portion for collecting inputfrom a user, the collection of input comprising causing the displayscreen generation portion to generate the one or more display screens;and a registration request portion for transmitting to the positionestimation server, via the communication portion, the registrationrequest information comprising one or more of a section, a structurename, signal intensity information, and estimated distance information.4. The wireless terminal of claim 3, wherein the one or more displayscreens comprise a section information registration screen forregistering information comprising section information with the positionestimation server, and a guidance screen.
 5. The wireless terminal ofclaim 4, wherein the section information registration screen comprisesmeans for inputting a structure name associated with the wirelessterminal's location, and a section associated with the wirelessterminal's location, the section comprising a floor or a room.
 6. Thewireless terminal of claim 3, wherein the display portion comprises atleast one of: a Cathode Ray Tube (CRT) display device, a Liquid CrystalDisplay (LCD) device, an Organic Light Emitting Display (OLED) device,and a lamp.
 7. The wireless terminal of claim 3, wherein the informationacquisition portion periodically transmits the at least one piece ofsecond measurement information, or transmits the measurement informationbased on user operation of the operation portion.
 8. The wirelessterminal of claim 3, wherein the communication portion comprises one ormore of: a wireless communication function defined by the Institute ofElectrical and Electronic Engineers (IEEE); a Multiple Input MultipleOutput (MIMO) communication function defined by IEEE; and acommunication function associated with Worldwide Interoperability forMicrowave Access (WiMAX).
 9. The wireless terminal of claim 3, whereinthe communication portion communicates information comprising at leastone of: electronic mail, audio data, visual data, and program code. 10.The wireless terminal of claim 3, wherein the wireless terminal is oneof: a mobile phone, a personal computer, a home video processing device,a personal handyphone system, a mobile music playback device, a mobilevideo processing device, a personal digital assistant, a home gameconsole, a mobile game console, and a household electrical appliance.